1. Field of the Invention
The present invention relates to a shoe for a hydraulic apparatus, and manufacturing method thereof.
2. Description of the Related Art
A conventional shoe used in a hydraulic apparatus such as a swash plate type axial piston pump and disposed between a piston and a swash plate was manufactured according to steps shown in FIGS. 36 through 47. Specifically, FIG. 36 shows a material to be processed, provided with a sliding-contact plate laminated on one surface thereof in one united body. FIGS. 37, 38 show two turning steps on an NC lathe; FIGS. 39, 40 show a process of welding a sphere to the main body; FIG. 41 shows a process of scraping an end portion of the sphere to make a bore; FIG. 42 shows a heat treatment (soft nitriding by gas) process and vibrating barrel process. The following FIGS. 43, 44 show two process of punching the sphere and the main body; FIG. 45 shows a process of scraping an end portion on an NC lathe; FIG. 46 shows a process of lapping a surface; and FIG. 47 shows a process of combining with a piston.
However, since such conventional manufacturing process consists of processing a main body laminated with a sliding-contact plate in order to manufacture a shoe, it has disadvantages such as large dimensions of the material to be processes, considerable material loss through the process, complication of manufacturing process, etc. all of which leads to a high production cost.
On the other hand, a method was proposed wherein a main body and a sliding-contact plate are separated, and the sliding-contact plate is processed to become a bimetal and fitted to the main body (as disclosed in JP-A No.2000-170645), however the sliding-contact plate is prone to come off from the main body because of vibration etc. during operation, since the sliding-contact plate is merely fitted to the main body. This could lead to an idea of welding the sliding-contact plate to the main body, but such method is not preferable either because the sliding-contact surface may become uneven owing to the welding process.